Soft absorbent tissue paper containing a biodegradable quaternized amine-ester softening compound and a temporary wet strength resin

ABSTRACT

Tissue paper webs useful in the manufacture of soft, absorbent products such as napkins, facial tissues, and sanitary tissues, and processes for making the webs. The tissue paper webs comprise papermaking fibers, a biodegradable quaternized amine-ester softening compound, a wetting agent, and a temporary wet strength resin. The process comprises a first step of forming an aqueous papermaking furnish from the above-mentioned components. The second and third steps in the basic process are the deposition of the papermaking furnish onto a foraminous surface such as a Fourdrinier wire and removal of the water from the deposited furnish. An alternate process involves the use of the furnish containing the aforementioned components in a papermaking process which will produce a pattern densified fibrous web having a relatively high bulk field of relatively low fiber density in a patterned array of spaced zones of relatively high fiber density.

FIELD OF THE INVENTION

This invention relates to tissue paper webs. More particularly, itrelates to soft, absorbent tissue paper webs which can be used insanitary tissue, facial tissue products, and paper napkins.

BACKGROUND OF THE INVENTION

Paper webs or sheets, sometimes called tissue or paper tissue webs orsheets, find extensive use in modern society. Such items as papertowels, napkins, and facial tissues are staple items of commerce. It haslong been recognized that three important physical attributes of theseproducts are their softness; their absorbency, particularly theirabsorbency for aqueous systems; and their strength, particularly theirstrength when wet. Research and development efforts have been directedto the improvement of each of these attributes without deleteriouslyaffecting the others as well as to the improvement of two or threeattributes simultaneously.

Softness is the tactile sensation perceived by the consumer as he/sheholds a particular product, rubs it across his/her skin, or crumples itwithin his/her hand. This tactile sensation is a combination of severalphysical properties. One of the more important physical propertiesrelated to softness is generally considered by those skilled in the artto be the stiffness of the paper web from which the product is made.Stiffness, in turn, is usually considered to be directly dependent onthe dry tensile strength of the web.

Strength is the ability of the product, and its constituent webs, tomaintain physical integrity and to resist tearing, bursting, andshredding under use conditions, particularly when wet.

Absorbency is the measure of the ability of a product, and itsconstituent webs, to absorb quantities of liquid, particularly aqueoussolutions or dispersions. Overall absorbency as perceived by the humanconsumer is generally considered to be a combination of the totalquantity of liquid a given mass of tissue paper will absorb atsaturation as well as the rate at which the mass absorbs the liquid.

The use of wet strength resins to enhance the strength of a paper web iswidely known. For example, Westfelt described a number of such materialsand discussed their chemistry in Cellulose Chemistry and Technology,Volume 13, at pages 813-825 (1979).

Freimark et al. in U.S. Pat. No. 3,755,220 issued Aug. 28, 1973 mentionthat certain chemical additives known as debonding agents interfere withthe natural fiber-to-fiber bonding that occurs during sheet formation inpapermaking processes. This reduction in bonding leads to a softer, orless harsh, sheet of paper. Freimark et al. go on to teach the use ofwet strength resins to enhance the wet strength of the sheet inconjunction with the use of debonding agents to off-set undesirableeffects of the debonding agents. These debonding agents do reduce drytensile strength, but there is also generally a reduction in wet tensilestrength.

Shaw, in U.S. Pat. No. 3,821,068, issued Jun. 28, 1974, also teachesthat chemical debonders can be used to reduce the stiffness, and thusenhance the softness, of a tissue paper web.

Chemical debonding agents have been disclosed in various references suchas U.S. Pat. No. 3,554,862, issued to Hervey et al . on Jan. 12, 1971.These materials include quaternary ammonium salts such astrimethylcocoammonium chloride, trimethyloleylammonium chloride,di(hydrogenated-tallow)dimethylammonium chloride andtrimethylstearylammonium chloride.

Emanuelsson et al., in U.S. Pat. No. 4,144,122, issued Mar. 13, 1979,teach the use of complex quaternary ammonium compounds such asbis(alkoxy-(2-hydroxy)-propylene) quaternary ammonium chlorides tosoften webs. These authors also attempt to overcome any decrease inabsorbency caused by the debonders through the use of nonionicsurfactants such as ethylene oxide and propylene oxide adducts of fattyalcohols.

Armak Company, of Chicago, Ill., in their bulletin 76-17 (1977) disclosethat the use of di(hydrogenated-tallow)dimethylammonium chloride incombination with fatty acid esters of polyoxyethylene glycols may impartboth softness and absorbency to tissue paper webs.

One exemplary result of research directed toward improved paper webs isdescribed in U.S. Pat. No. 3,301,746, issued to Sanford and Sisson onJan. 31, 1967. Despite the high quality of paper webs made by theprocess described in this patent, and despite the commercial success ofproducts formed from these webs, research efforts directed to findingimproved products have continued.

For example, Becker et al. in U.S. Pat. No. 4,158,594, issued Jan. 19,1979, describe a method they contend will form a strong, soft, fibroussheet. More specifically, they teach that the strength of a tissue paperweb (which may have been softened by the addition of chemical debondingagents) can be enhanced by adhering, during processing, one surface ofthe web to a creping surface in a fine patterned arrangement by abonding material (such as an acrylic latex rubber emulsion, a watersoluble resin, or an elastomeric bonding material) which has beenadhered to one surface of the web and to the creping surface in the finepatterned arrangement, and creping the web from the creping surface toform a sheet material.

Conventional quaternary ammonium compounds such as the well knowndialkyldimethylamonium salts (e.g., ditallowdimethylammonium chloride,ditallowdimethyammonium methylsulfate, di(hydrogenated tallow)dimethylammonium chloride, etc.) are effective chemical debonding agents.Unfortunately, these quaternary ammonium compounds are notbiodegradable. Applicant has discovered that biodegradable mono- anddiester variations of these quaternary ammonium salts also functioneffectively as chemical debonding agents and enhance the softness oftissue paper webs.

It is an object of this invention to provide a process for making soft,absorbent tissue paper webs with high temporary wet strength.

It is a further object of this invention to provide soft, absorbenttissue paper sheets with high temporary wet strength and that arebiodegradable.

It is a still further object of this invention to provide soft,absorbent sanitary tissue products with high temporary wet strength andthat are biodegradable.

These and other objects are obtained using the present invention, aswill become readily apparent from a reading of the following disclosure.

SUMMARY OF THE INVENTION

The present invention provides soft, absorbent tissue paper webs havinghigh temporary strength, and a process for making the webs. Briefly, thetissue paper webs comprise:

(a) papermaking fibers;

(b) from about 0.01% to about 2.0% by weight of a quaternizedamine-ester compound having the formula ##STR1## and mixtures thereof;wherein each R substituent is a C₁ -C₆ alkyl or hydroxyalkyl group, ormixtures thereof; R¹ is ##STR2## or a C₁₃ -C₁₉ hydrocarbyl group ormixtures thereof; R² is a C₁₃ -C₂₁ hydrocarbyl group or mixturesthereof; and X⁻ is a compatible anion;

(c) from about 0.01% to about 2.0% by weight of a wetting agent; and

(d) from about 0.01% to about 3.0% by weight of a water-solubletemporary wet strength resin.

Examples of quaternized amine-ester softening compounds suitable for usein the present invention include compounds having the formulas: ##STR3##

These compounds can be considered to be mono- and di- ester variationsof the well-known dialkyldimethylammonium salts such asditallowdimethylammonium chloride, ditallowdimethylammoniummethylsulfate, di(hydrogenated tallow)dimethylammonium chloride, withthe diester variations of di(hydrogenated tallow)dimethylammoniummethylsulfate and di(hydrogenated tallow)dimethylammonium chloride beingpreferred. Without being bound by theory, it is believed that the estermoiety(ies) lends biodegradability to these compounds.

Examples of wetting agents useful in the present invention includepolyhydroxy compounds such as glycerol and polyethylene glycols having amolecular weight of from about 200 to about 2000, with polyethyleneglycols having a molecular weight of from about 200 to about 600 beingpreferred. Other examples of suitable wetting agents include alkoxylatedalcohols, with linear alkoxylated alcohols and linear alkyl phenoxylatedalcohols being preferrred.

The temporary wet strength resins useful in the present inventioninclude all those commonly used in papermaking. Examples of preferredtemporary wet strength resins include cationic starch-based resins andthe cationic polymers described in U.S. Pat. No. 4,981,557, Bjorkquist,issued Jan. 1, 1991.

A particularly preferred tissue paper embodiment of the presentinvention comprises from about 0.01% to about 0.5% by weight of thequaternized amine-ester softening compound, from about 0.01% to about0.5% by weight of the wetting agent, and from about 0.1% to about 1.5%by weight of the water-soluble temporary wet strength resin, allquantities of these additives being on a dry fiber weight basis of thetissue paper.

Briefly, the process for making the tissue webs of the present inventioncomprises the steps of forming a papermaking furnish from theaforementioned components, deposition of the papermaking furnish onto aforaminous surface such as a Fourdrinier wire, and removal of the waterfrom the deposited furnish.

All percentages, ratios and proportions herein are by weight unlessotherwise specified.

The present invention is described in more detail below.

DETAILED DESCRIPTION OF THE INVENTION

While this specification concludes with claims particularly pointing outand distinctly claiming the subject matter regarded as the invention, itis believed that the invention can be better understood from a readingof the following detailed description and of the appended examples.

As used herein, the terms tissue paper web, paper web, web, and papersheet all refer to sheets of paper made by a process comprising thesteps of forming an aqueous papermaking furnish, depositing this furnishon a foraminous surface, such as a Fourdrinier wire, and removing thewater from the furnish as by gravity or vacuum-assisted drainage, withor without pressing, and by evaporation.

As used herein, an aqueous papermaking furnish is an aqueous slurry ofpapermaking fibers and the chemicals described hereinafter.

The first step in the process of this invention is the forming of anaqueous papermaking furnish. The furnish comprises papermaking fibers(hereinafter sometimes referred to as wood pulp), at least one wetstrength resin, at least one quaternary ammonium and at least onewetting agent, all of which will be hereinafter described.

It is anticipated that wood pulp in all its varieties will normallycomprise the papermaking fibers used in this invention. However, othercellulosic fibrous pulps, such as cotton linters, bagasse, rayon, etc.,can be used and none are disclaimed. Wood pulps useful herein includechemical pulps such as Kraft, sulfite and sulfate pulps as well asmechanical pulps including for example, ground wood, thermomechanicalpulps and chemically modified thermomechanical pulp (CTMP). Pulpsderived from both deciduous (e.g., Eucalyptus pulp) and coniferous trees(e.g., spruce) can be used. Also applicable to the present invention arefibers derived from recycled paper, which may contain any or all of theabove categories as well as other non-fibrous materials such as fillersand adhesives used to facilitate the original papermaking. Preferably,the papermaking fibers used in this invention comprise Kraft pulpderived from northern softwoods.

Wet Strength Resins

The present invention contains as an essential component from about0.01% to about 3.0%, more preferably from about 0.1% to about 1.5% byweight, on a dry fiber weight basis, of a water-soluble temporary wetstrength resin.

Wet strength resins useful herein can be of several types. Generally,those resins which have previously found and which will hereafter findutility in the papermaking art are useful herein. Numerous examples areshown in the aforementioned paper by Westfelt, incorporated herein byreference.

In the usual case, the wet strength resins are water-soluble, cationicmaterials. That is to say, the resins are water-soluble at the time theyare added to the papermaking furnish. It is quite possible, and even tobe expected, that subsequent events such as cross-linking will renderthe resins insoluble in water. Further, some resins are soluble onlyunder specific conditions, such as over a limited pH range.

Wet strength resins are generally believed to undergo a cross-linking orother curing reactions after they have been deposited on, within, oramong the papermaking fibers. Cross-linking or curing does not normallyoccur so long as substantial amounts of water are present.

Of particular utility are the various polyamide-epichlorohydrin resins.These materials are low molecular weight polymers provided with reactivefunctional groups such as amino, epoxy, and azetidinium groups. Thepatent literature is replete with descriptions of processes for makingsuch materials. U.S. Pat. No. 3,700,623, issued to Keim on Oct. 24, 1972and U.S. Pat. No. 3,772,076, issued to Keim on Nov. 13, 1973 areexamples of such patents and both are incorporated herein by reference.

Polyamide-epichlorohydrin resins sold under the trademarks Kymene 557Hand Kymene LX by Hercules Incorporated of Wilmington, Del., areparticularly useful in this invention. These resins are generallydescribed in the aforementioned patents to Keim.

Base-activated polyamide-epichlorohydrin resins useful in the presentinvention are sold under the Santo Res trademark, such as Santo Res 31,by Monsanto Company of St. Louis, Mo. These types of materials aregenerally described in U.S. Pat. Nos. 3,855,158 issued to Petrovich onDec. 17, 1974; 3,899,388 issued to Petrovich on Aug. 12, 1975; 4,129,528issued to Petrovich on Dec. 12, 1978; 4,147,586 issued to Petrovich onApr. 3, 1979; and 4,222,921 issued to Van Eenam on Sep. 16, 1980, allincorporated herein by reference.

Other water-soluble cationic resins useful herein are the polyacrylamideresins such as those sold under the Parez trademark, such as Parez631NC, by American Cyanamid Company of Stanford, Conn. These materialsare generally described in U.S. Pat. Nos. 3,556,932 issued to Coscia etal. on Jan. 19, 1971; and 3,556,933 issued to Williams et al. on Jan.19, 1971, all incorporated herein by reference.

Other types of water-soluble resins useful in the present inventioninclude acrylic emulsions and anionic styrene-butadiene latexes.Numerous examples of these types of resins are provided in U.S. Pat. No.3,844,880, Meisel, Jr. et al., issued Oct. 29, 1974, incorporated hereinby reference.

Still other water-soluble cationic resins finding utility in thisinvention are the urea formaldehyde and melamine formaldehyde resins.These polyfunctional, reactive polymers have molecular weights on theorder of a few thousand. The more common functional groups includenitrogen containing groups such as amino groups and methylol groupsattached to nitrogen.

Although less preferred, polyethylenimine type resins find utility inthe present invention.

More complete descriptions of the aforementioned water-soluble resins,including their manufacture, can be found in TAPPI Monograph Series No.29, Wet Strength In Paper and Paperboard, Technical Association of thePulp and Paper Industry (New York; 1965), incorporated herein byreference.

The above-mentioned wet strength additives typically result in paperproducts with permanent wet strength, i.e., paper which when placed inan aqueous medium retains a substantial portion of its initial wetstrength over time. However, permanent wet strength in some types ofpaper products can be an unnecessary and undesirable property. Paperproducts such as toilet tissues, etc., are generally disposed of afterbrief periods of use into septic systems and the like. Clogging of thesesystems can result if the paper product permanently retains itshydrolysis-resistant strength properties.

More recently, manufacturers have added temporary wet strength additivesto paper products for which wet strength is sufficient for the intendeduse, but which then decays upon soaking in water. Decay of the wetstrength facilitates flow of the paper product through septic systems.As used herein, the term "temporary wet strength resin" refers to aresin that allows the tissue paper, when placed in an aqueous medium, tolose a majority of its initial wet strength in a short period of time,e.g., two minutes or less, more preferably, 30 seconds or less.

Examples of suitable temporary wet strength resins include modifiedstarch temporary wet strength agents such as National Starch 78-0080,marketed by the National Starch and Chemical Corporation (New York,N.Y.). This type of wet strength agent can be made by reactingdimethoxyethyl-N-methyl-chloroacetamide with cationic starch polymers.Modified starch temporary wet strength agents are also described in U.S.Pat. No. 4,675,394, Solarek, et al., issued Jun. 23, 1987, andincorporated herein by reference.

Preferred temporary wet strength resins include those described in U.S.Pat. No. 4,981,557, Bjorkquist, issued Jan. 1, 1991, and incorporatedherein by reference. The temporary wet strength resins described in U.S.Pat. No. 4,981,557 comprise a polymer characterized by the substantiallycomplete absence of nucleophilic functionalities and having the formula:##STR4## wherein: A is ##STR5## and X is --O--, --NCH₃ --, and R is asubstituted or unsubstituted aliphatic groups; Y₁ and Y₂ areindependently --H, --CH₃ or a halogen; W is a nonnucleophilic,water-soluble nitrogen heterocyclic moiety; C is a cationic monomericunit; the mole percent of a is from about 30% to about 70%, the molepercent of b is from about 30% to about 70%, and the mole percent of cis from about 1% to about 40%; and said polymer has an average molecularweight of between about 30,000 and about 200,000.

With respect to the classes and specific examples of both permanent andtemporary wet strength resins listed above, it should be understood thatthe resins listed are exemplary in nature and are not meant to limit thescope of this invention.

Mixtures of compatible wet strength resins, such as the temporary wetstrength resins described in U.S. Pat. No. 4,981,557 and the modifiedstarch temporary wet strength resins described above, can also be usedin the practice of this invention.

Quaternized Amine-Ester Softening Compound

The present invention contains as an essential component from about0.01% to about 2.0%, more preferably from about 0.01% to about 0.5% byweight, on a dry fiber weight basis, of a quaternized amine-estersoftening compound having the formula: ##STR6## and mixtures thereof;wherein each R substituent is a short chain (C₁ -C₆, preferably C₁ -C₃)alkyl or hydroxyalkyl group, e.g., methyl (most preferred), ethyl,propyl, hydroxyethyl, and the like, or mixtures thereof; R¹ is ##STR7##or a long chain C₁₃ -C₁₉ hydrocarbyl substituent, preferably C₁₆ -C₁₈alkyl, most preferably straight-chain C₁₈ alkyl ; R² is a long chain C₁₃-C₂₁ hydrocarbyl substituent, preferably C₁₃ -C₁₇ alkyl, most preferablyC₁₅ straight chain alkyl. The counterion X⁻ is not critical herein, andcan be any softener-compatible anion, such as an halide (e.g., chlorideor bromide), or methylsulfate. Preferably, X⁻ is methyl sulfate orchloride. It will be understood that substituents R, R¹ and R² mayoptionally be substituted with various groups such as alkoxyl, hydroxyl,or can be branched, but such materials are not preferred herein. Thepreferred compounds can be considered to be mono- and di- estervariations of the well-known dialkyldimethylammonium salts such asditallowdimethylammonium chloride, ditallowdimethylammoniummethylsulfate, di(hydrogenated tallow)dimethylammonium chloride, withthe diester variations of di(hydrogenatedtallow)dimethylammoniummethylsulfate or di(hydrogenated tallow)dimethylammonium chloride beingpreferred.

Tallow is a naturally occurring material having a variable composition.Swern, Ed. in Bailey's Industrial Oil and Fat Products, Third Edition,John Wiley and Sons (New York 1964) in Table 6.13, indicates thattypically 78% or more of the fatty acids of tallow contain 16 or 18carbon atoms. Typically, half of the fatty acids present in tallow areunsaturated, primarily in the form of oleic acid. Synthetic as well asnatural "tallows" fall within the scope of the present invention.

The above compounds used as the active softener ingredient in thepractice of this invention are prepared using standard reactionchemistry. For example, in a typical synthesis of a monoester variationof a dialkyldimethylammonium salt, an amine of the formula RR¹ NCH₂ CH₂OH is esterified at the hydroxyl group with an acid chloride of theformula R² C(O)Cl, then quaternized with an alkyl halide, RX, to yieldthe desired reaction product (wherein R, R¹, and R² are as defined inthe present application). A method for the synthesis of a preferredmono-ester softening compound is disclosed in detail hereinafter.However, it will be appreciated by those skilled in the chemical artsthat this reaction sequence allows a broad selection of compounds to beprepared. As illustrative, nonlimiting examples there can be mentionedthe following quaternized amine monoesters (wherein all long-chain alkylsubstituents are straight-chain):

[CH₃ ]₂ [CH₁₈ H₃₇ ]⁺ NCH₂ CH₂ OC(O)C₁₅ H₃₁ Br⁻

[CH₃ ]₂ [CH₁₃ H₂₇ ]⁺ NCH₂ CH₂ OC(O)C₁₇ H₃₅ Cl⁻

[C₂ H₅ ]₂ [C₁₇ H₃₅ ]⁺ NCH₂ CH₂ OC(O)C₁₃ H₂₇ Cl⁻

[C₂ H₅ ][CH₃ ][C₁₈ H₃₇ ⁺ NCH₂ CH₂ OC(O)C₁₄ H₂₉ CH₃ SO₄ ⁻

[C₃ H₇ ][C₂ H₅ ][C₁₆ H₃₃ ]⁺ NCH₂ CH₂ OC(O)C₁₅ H₃₁ Cl⁻

[iso-C₃ H₇ ][CH₃ ][CH₁₈ H₃₇ ]⁺ NCH₂ CH₂ OC(O)C₁₅ H₃₁ Cl⁻

Similarly, in a typical synthesis of a diester variation of adialkyldimethylammonium salt, an amine of the formula RN(CH₂ CH₂ OH)₂ isesterified at both hydroxyl groups with an acid chloride of the formulaR² C(O)Cl, then quaternized with an alkyl halide, RX, to yield thedesired reaction product (wherein R and R² are as defined in the presentapplication). A method for the synthesis of a preferred di-estersoftening compound is disclosed in detail hereinafter. However, it willbe appreciated by those skilled in the chemical arts that this reactionsequence allows a broad selection of compounds to be prepared. Asillustrative, nonlimiting examples there can be mentioned the following(wherein all long-chain alkyl substituents are straight-chain):

[HO-CH(CH₃)CH₂ ][CH₃ ]⁺ N[CH₂ CH₂ OC(O)C₁₅ H₃₁ ]₂ Br⁻

[C₂ H₅ ]₂ ⁺ N[CH₂ CH₂ OC(O)C₁₇ H₃₅ ]₂ Cl⁻

[CH₃ ][C₂ H₅ ]⁺ N[CH₂ CH₂ OC(O)C₁₃ H₂₇ ]₂ l⁻

[C₃ H₇ ][C₂ H₅ ]⁺ N[CH₂ CH₂ OC(O)C₁₅ H₃₁ ]₂ SO₄ ⁻ CH₃ ##STR8##

Synthesis of a guaternized amine monoester softening compound

Synthesis of the preferred biodegradable, quaternized amine monoestersoftening compound used herein is accomplished by the following two-stepprocess: ##STR9## 0.6 mole of octadecyl ethanol methyl amine is placedin a 3-liter, 3-necked flask equipped with a reflux condenser, argon (ornitrogen) inlet and two addition funnels. In one addition funnel isplaced 0.4 moles of triethylamine and in the second addition funnel isplaced 0.6 mole of palmitoyl chloride in a 1:1 solution with methylenechloride. Methylene chloride (750 mL is added to the reaction flaskcontaining the amine and heated to 35° C. (water bath). Thetriethylamine is added dropwise, and the temperature is raised to40°-45° C. while stirring over one-half hour. The palmitoylchloride/methylene chloride solution is added dropwise and allowed toheat at 40°-45° C. under inert atmosphere overnight (12-16 h).

The reaction mixture is cooled to room temperature and diluted withchloroform (1500 mL). The chloroform solution of product is placed in aseparatory funnel (4 L) and washed with sat. NaCl, dil. CA(OH)₂, 50% K₂CO₃ (3 times)*, and, finally, sat. NaCl. The organic layer is collectedand dried over MgSO₄, filtered and solvents are removed via rotaryevaporation. Final drying is done under high vacuum (0.25 mm Hg).

ANALYSIS

TLC (thin layer chromoatography)**: solvent system (75% diethyl ether:25% hexane) Rf=0.7.

IR (CCl₄): 2910, 2850, 2810, 2760, 1722, 1450, 1370 cm⁻¹

¹ H-NMR (CDCl₃): δ2.1-2.5 (8H), 2.1 (3H), 1.20 (58H), 0.9 (6H) ppm(relative to tetramethylsilane=0 ppm). ##STR10## 0.5 mole of theoctadecyl palmitoyloxyethyl methyl amine, prepared in Step A, is placedin an autoclave sleeve along with 200-300 mL of acetonitrile(anhydrous). The sample is then inserted into the autoclave and purgedthree times with He (16275 mm Hg/21.4 ATM.) and once with CH₃ Cl. Thereaction is heated to 80° C. under a pressure of 3604 mm Hg/4.7 ATM. CH₃Cl and solvent is drained from the reaction mixture. The sample isdissolved in chloroform and solvent is removed by rotary evaporation,followed by drying on high vacuum (0.25 mm Hg). Both the C₁₈ H₃₇ and C₁₅H₃₁ substituents in this highly preferred compound are n-alkyl.

ANALYSIS

TLC (5:1 chloroform:methanol)*: Rf=0.25.

IR (CCl₄): 2910, 2832, 1730, 1450 cm⁻¹.

¹ H-NMR (CDCl₃): δ4.0-4.5 (2H), 3.5 (6H), 2.0-2.7 (6H), 1.2-1.5 (58H),0.9 (6H) ppm (relative to tetramethylsilane=0 ppm).

¹³ C-NMR (CDCl₃) δ172.5, 65.3, 62.1, 57.4, 51.8, 33.9, 31.8, 29.5, 28.7,26.2, 22.8, 22.5, 14.0 (relative to tetramethylsilane=0 ppm).

Synthesis of a guaternized amine di-ester softening compound

The preferred biodegradable, quaternized amine diester fabric softeningcompound used in the present invention may be synthesized using thefollowing two-step process: ##STR11## 0.6 mole of methyl diethanol amineis placed in a 3-liter, 3-necked flask equipped with a reflux condenser,argon (or nitrogen) inlet and two addition funnels. In one additionfunnel is placed 0.8 moles of triethylamine and in the second additionfunnel is placed 1.2 moles of palmitoyl chloride in a 1:1 solution withmethylene chloride. Methylene chloride (750 mL) is added to the reactionflask containing the amine and heated to about 35° C. (water bath). Thetriethylamine is added dropwise, and the temperature is raised to40°-45° C. while stirring over one-half hour. The palmitoylchloride/methylene chloride solution is added dropwise and allowed toheat at 40°-45° C. under inert atmosphere overnight (12-16 h).

The reaction mixture is cooled to room temperature and diluted withchloroform (1500 mi). The chloroform solution of product is placed in aseparatory funnel (4 L) and washed with sat. NaCl, dil. CA(OH)₂, 50% K₂CO₃ (3 times)*, and, finally, sat. NaCl. The organic layer is collectedand dried over MgSO₄ and filtered. Solvents are removed via rotaryevaoporation. Final drying is done under high vacuum (0.25 mm Hg).

ANALYSIS

TLC (thin layer chromatography)**: solvent system (75% diethyl ether:25% hexane) Rf=0.75.

IR (CCl₄): 2920, 2850, 1735, 1450, 1155, 1100 cm⁻¹.

¹ H-NMR (CDCl₃): δ3.9-4.1 (2H), 2.1-2.8 (8H), 2.3 (3H), 1.25 (52H), 1.1(6H), 0.8 (6H) ppm (relative to tetramethylsilane=0 ppm).

Step B: Ouaternization ##STR12## 0.5 moles of the methyl diethanolpalmitate amine from Step A is placed in an autoclave sleeve along with200-300 mL of acetonitrile (anhydous). The sample is then inserted intothe autoclave and purged three times with He (16275 mm Hg/21.4 ATM.) andonce with CH₃ Cl. The reaction is heated to 80° C. under a pressure of3604 mm Hg/4.7 ATM. CH₃ Cl for 24 hours. The autoclave sleeve is thenremoved from the reaction mixture. The sample is dissolved in chloroformand solvent is removed by rotary evaporation, followed by drying on highvacuum (0.25 mm Hg). ANALYSIS

TLC (5:1 chloroform:methanol)*: Rf=0.35.

IR (CCl₄): 2915, 2855, 1735, 1455, 1150 cm⁻¹.

¹ H-NMR (CDCl₃): δ4.5-5.0 (2H), 4.0-4.4 (4H), 3.7 (6H), 2.0-2.5 (4H),1.2-1.5 (52H), 0.9 (6H) ppm (relative to tetramethylsilane=0 ppm).

¹³ C-NMR (CDCl₃); δ172.8, 63.5, 57.9, 52.3, 33.8, 31.8, 31.4, 29.6224.6, 22.6, 14.1 ppm (relative to tetramethylsilane=0 ppm).

Although one skilled in the art can prepare the active softeneringredient using standard reaction chemistry, as illustrated above,various quaternized amine-ester compounds are also availablecommercially under the tradenames SYNPROLAM FS from ICI and REWOQUATfrom REWO. A preferred quaternized amine-ester softening compound, i.e.,the diester of di(hydrogenated tallow)dimethyl ammonium chloride, isavailable commercially from the Sherex Chemical Company Inc. of Dublin,Ohio under the tradename "Adogen DDMC".

Wetting Agent

The present invention contains as an essential component from 0.01% toabout 2.0%, more preferably from about 0.01% to about 0.5% by weight, ona dry fiber weight basis, of a wetting agent.

Examples of wetting agents useful in the present invention includepolyhydroxy compounds such as glycerol and polyethylene glycols having amolecular weight of from about 200 to about 2000, with polyethyleneglycols having a molecular weight of from about 200 to about 600 beingpreferred.

A particularly preferred polyhydroxy wetting agent is polyethyleneglycol having a molecular weight of about 400. This material isavailable commercially from the Union Carbide Company of Danbury, Conn.under the tradename "PEG-400".

Other types of wetting agents useful in the present invention includealkoxylated alcohols. Preferably, the alkoxylated alcohol wetting agentsare selected from the group consisting of linear alkoxylated alcohols,linear alkyl phenoxylated alcohols, and mixtures thereof. Mostpreferably, the alkoxylated is a linear ethoxylated alcohol or a linearalkyl phenoxypoly(ethyleneoxy) alcohol.

Specific linear ethoxylated alcohols useful in the present invention areselected from the group consisting of the condensation products of C₈-C₁₈ linear fatty alcohols with from about 1 to 10 moles of ethyleneoxide and mixtures thereof. Examples of linear ethoxylated alcohols ofthis type include Neodol 23-3 (the condensation product of C₁₂ -C₁₃linear alcohol with 3 moles ethylene exide), Neodol 91-2.5 (thecondensation product of C₉ -C₁₁ linear alcohol with 2.5 moles ethyleneoxide), Neodol 45-9 (the condensation product of C₁₄ -C₁₅ linear alcoholwith 9 moles ethylene oxide), Neodol 45-7 (the condensation product ofC₁₄ -C₁₅ linear alcohol with 7 moles ethylene oxide), Neodol 45-4 (thecondensation product of C₁₄ -C₁₅ linear alcohol with 4 moles ethyleneoxide), all of which are marketed by Shell Chemical Company. Preferredare the condensation products of C₁₀ -C₁₅ linear alcohols with fromabout 4 to 8 moles of ethylene oxide, most preferred are thecondensation products of C₁₂ -C₁₃ linear alcohols with 7 moles ethyleneoxide (e.g., Neodol 23-7).

Specific linear alkyl phenoxypoly(ethyleneoxy) alcohols useful in thepresent invention are selected from the group consisting of thecondensation products of C₈ -C₁₈ alkyl phenoxy fatty alcohols with fromabout 1 to 10 moles of ethylene oxide and mixtures thereof. Examples ofalkyl phenoxypoly(ethyleneoxy) alcohols of this type include IgepalRC-520, Igepal RC-620, Igepal DM-530, Igepal CTA-639W, all of which aremarketed by the Rhone Poulenc Corporation (Cranbury, N.J.). Mostpreferred are Igepal RC-520 and RC-620.

Optional Ingredients

Other chemicals commonly used in papermaking can be added to thepapermaking furnish so long as they do not significantly and adverselyaffect the softening, absorbency, and wet strength enhancing actions ofthe three required chemicals.

For example, surfactants may be used to treat the tissue paper webs ofthe present invention. The level of surfactant, if used, is preferablyfrom about 0.01% to about 2.0% by weight, based on the dry fiber weightof the tissue paper. The surfactants preferably have alkyl chains witheight or more carbon atoms. Exemplary anionic surfactants are linearalkyl sulfonates, and alkylbenzene sulfonates. Exemplary nonionicsurfactants are alkylglycosides including alkylglycoside esters such asCrodesta™ SL-40 which is available from Croda, Inc. (New York, N.Y.);alkylglycoside ethers as described in U.S. Pat. No. 4.011,389, issued toW. K. Langdon, et al. on Mar. 8, 1977.

Other types of chemicals which may be added include dry strengthadditives to increase the tensile strength of the tissue webs. Examplesof dry strength additives include cationic polymers from the ACCOchemical family such as ACCO 771 and ACCO 514. The level of dry strengthadditive, if used, is preferably from about 0.01% to about 1.0%, byweight, based on the dry fiber weight of the tissue paper.

The above listings of additional chemical additives is intended to bemerely exemplary in nature, and are not meant to limit the scope of theinvention.

The papermaking furnish can be readily formed or prepared by mixingtechniques and equipment well known to those skilled in the papermakingart.

The three types of chemical ingredients described above, i.e.,quaternized amine-ester softening compounds, wetting agents, and watersoluble temporary wet strength resins, are preferably added to theaqueous slurry of papermaking fibers, or furnish in the wet end of thepapermaking machine at some suitable point ahead of the Fourdrinier wireor sheet forming stage. However, applications of the above chemicalingredients subsequent to formation of a wet tissue web and prior todrying of the web to completion will also provide significant softness,absorbency, and wet strength benefits and are expressly included withinthe scope of the present invention.

It has been discovered that the chemical ingredients are more effectivewhen the quaternized amine-ester compound and the wetting agent arefirst premixed together before being added to the papermaking furnish. Apreferred method, as will be described in greater detail hereinafter inExample 1, consists of first heating the wetting agent to a temperatureof about 180° F., and then adding the quaternized amine-ester compoundto the hot wetting agent to form a fluidized "melt". Preferably, themolar ratio of the quaternized amine-ester compound to the wetting agentis about 1 to 1, although this ratio will vary depending upon themolecular weight of the particular wetting agent and/or quaternizedamine-ester compound used. The quaternized amine-ester compound andwetting agent melt is then diluted to the desired concentration, andmixed to form an aqueous vesicle solution which is then added to thepapermaking furnish.

Since the quaternized amine-ester compounds (both mono- and di-esters)are somewhat labile to hydrolysis, they should be handled rathercarefully when diluted to the desired concentrations. For example,stable diluted liquid compositions herein are formulated at a pH in therange of about 2.0 to about 5.0, preferably about pH 3.0±0.5. The pH canbe adjusted by the addition of a Bronsted acid. Examples of suitableBronsted acids include the inorganic mineral acids, carboxylic acids, inparticular the low molecular weight (C₁ -C₅) carboxylic acids, andalkylsulfonic acids. Suitable inorganic acids include HCl, H₂ SO₄, HNO₃and H₃ PO₄. Suitable organic acids include formic, acetic,methylsulfonic and ethylsulfonic acid. Preferred acids are hydrochloricand phosphoric acids.

Without being bound by theory, it is believed that the wetting agentenhances the flexibility of the cellulosic fibers, improves theabsorbency of the fibers, and acts to stabilize the quaternizedamine-ester compound in the aqueous solution. Separately, the temporarywet strength resins are also diluted to the appropriate concentrationand added to the papermaking furnish. The quaternizedamine-ester/wetting agent chemical softening composition acts to makethe paper product soft and absorbent, while the temporary wet strengthresin insures that the resulting paper product also has high temporarywet strength. In other words, the present invention makes it possible tonot only improve both the softness and absorbent rate of the tissuewebs, but also provides a high level of temporary wet strength.

The second step in the process of this invention is the depositing ofthe papermaking furnish on a foraminous surface and the third is theremoving of the water from the furnish so deposited. Techniques andequipment which can be used to accomplish these two processing stepswill be readily apparent to those skilled in the papermaking art.

The present invention is applicable to tissue paper in general,including but not limited to conventionally felt-pressed tissue paper;pattern densified tissue paper such as exemplified in the aforementionedU.S. Patent by Sanford-Sisson and its progeny; and high bulk,uncompacted tissue paper such as exemplified by U.S. Pat. No. 3,812,000,Salvucci, Jr., issued May 21, 1974. The tissue paper may be of ahomogenous or multilayered construction; and tissue paper products madetherefrom may be of a single-ply or multi-ply construction. The tissuepaper preferably has a basis weight of between 10 g/m² and about 65g/m², and density of about 0.60 g/cc or less. More preferably, basisweight will be below about 35 g/m² or less; and density will be about0.30 g/cc or less. Most preferably, density will be between 0.04 g/ccand about 0.20 g/cc.

Conventionally pressed tissue paper and methods for making such paperare known in the art. Such paper is typically made by depositing thepapermaking furnish on a foraminous forming wire. This forming wire isoften referred to in the art as a Fourdrinier wire. Once the furnish isdeposited on the forming wire, it is referred to as a web. The web isdewatered by pressing the web and drying at elevated temperature. Theparticular techniques and typical equipment for making webs according tothe process just described are well known to those skilled in the art.In a typical process, a low consistency pulp furnish is provided in apressurized headbox. The headbox has an opening for delivering a thindeposit of pulp furnish onto the Fourdrinier wire to form a wet web. Theweb is then typically dewatered to a fiber consistency of between about7% and about 25% (total web weight basis) by vacuum dewatering andfurther dried by pressing operations wherein the web is subjected topressure developed by opposing mechanical members, for example,cylindrical rolls. The dewatered web is then further pressed and driedby a stream drum apparatus known in the art as a Yankee dryer. Pressurecan be developed at the Yankee dryer by mechanical means such as anopposing cylindrical drum pressing against the web. Multiple Yankeedryer drums may be employed, whereby additional pressing is optionallyincurred between the drums. The tissue paper structures which are formedare referred to hereinafter as conventional, pressed, tissue paperstructures. Such sheets are considered to be compacted since the web issubjected to substantial mechanical compressional forces while thefibers are moist and are then dried while in a compressed state.

Pattern densified tissue paper is characterized by having a relativelyhigh bulk field of relatively low fiber density and an array ofdensified zones of relatively high fiber density. The high bulk field isalternatively characterized as a field of pillow regions. The densifiedzones are alternatively referred to as knuckle regions. The densifiedzones may be discretely spaced within the high bulk field or may beinterconnected within the high bulk field. Preferred processes formaking pattern densified tissue webs are disclosed in U.S. Pat. No.3,301,746, issued to Sanford and Sisson on Jan. 31, 1967, U.S. Pat. No.3,974,025, issued to Peter G. Ayers on Aug. 10, 1976, and U.S. Pat. No.4,191,609, issued to Paul D. Trokhan on Mar. 4, 1980, and U.S. Pat. No.4,637,859, issued to Paul D. Trokhan on Jan. 20, 1987; all of which areincorporated herein by reference.

In general, pattern densified webs are preferably prepared by depositinga papermaking furnish on a foraminous forming wire such as a Fourdrinierwire to form a wet web and then juxtaposing the web against an array ofsupports. The web is pressed against the array of supports, therebyresulting in densified zones in the web at the locations geographicallycorresponding to the points of contact between the array of supports andthe wet web. The remainder of the web not compressed during thisoperation is referred to as the high bulk field. This high bulk fieldcan be further dedensified by application of fluid pressure, such aswith a vacuum type device or a blow-through dryer, or by mechanicallypressing the web against the array of supports. The web is dewatered,and optionally predried, in such a manner so as to substantially avoidcompression of the high bulk field. This is preferably accomplished byfluid pressure, such as with a vacuum type device or blow-through dryer,or alternately by mechanically pressing the web against an array ofsupports wherein the high bulk field is not compressed. The operationsof dewatering, optional predrying and formation of the densified zonesmay be integrated or partially integrated to reduce the total number ofprocessing steps performed. Subsequent to formation of the densifiedzones, dewatering, and optional predrying, the web is dried tocompletion, preferably still avoiding mechanical pressing. Preferably,from about 8% to about 55% of the tissue paper surface comprisesdensified knuckles having a relative density of at least 125% of thedensity of the high bulk field.

The array of supports is preferably an imprinting carrier fabric havinga patterned placement of knuckles which operate as the array of supportswhich facilitate the formation of the densified zones upon applicationof pressure. The pattern of knuckles constitutes the array of supportspreviously referred to. Imprinting carrier fabrics are disclosed in U.S.Pat. No. 3,301,746, Sanford and Sisson, issued Jan. 31, 1967, U.S. Pat.No. 3,821,068, Salvucci, Jr. et al., issued May 21, 1974, U.S. Pat. No.3,974,025, Ayers, issued Aug. 10, 1976, U.S. Pat. No. 3,573,164,Friedberg et al., issued Mar. 30, 1971, U.S. Pat. No. 3,473,576, Amneus,issued Oct. 21, 1969, U.S. Pat. No. 4,239,065, Trokhan, issued Dec. 16,1980, and U.S. Pat. No. 4,528,239, Trokhan, issued Jul. 9, 1985, all ofwhich are incorporated herein by reference.

Preferably, the furnish is first formed into a wet web on a foraminousforming carrier, such as a Fourdrinier wire. The web is dewatered andtransferred to an imprinting fabric. The furnish may alternately beinitially deposited on a foraminous supporting carrier which alsooperates as an imprinting fabric. Once formed, the wet web is dewateredand, preferably, thermally predried to a selected fiber consistency ofbetween about 40% and about 80%. Dewatering is preferably performed withsuction boxes or other vacuum devices or with blow-through dryers. Theknuckle imprint of the imprinting fabric is impressed in the web asdiscussed above, prior to drying the web to completion. One method foraccomplishing this is through application of mechanical pressure. Thiscan be done, for example, by pressing a nip roll which supports theimprinting fabric against the face of a drying drum, such as a Yankeedryer, wherein the web is disposed between the nip roll and drying drum.Also, preferably, the web is molded against the imprinting fabric priorto completion of drying by application of fluid pressure with a vacuumdevice such as a suction box, or with a blow-through dryer. Fluidpressure may be applied to induce impression of densified zones duringinitial dewatering, in a separate, subsequent process stage, or acombination thereof.

Uncompacted, nonpattern-densified tissue paper structures are describedin U.S. Pat. No. 3,812,000 issued to Joseph L. Salvucci, Jr. and PeterN. Yiannos on May 21, 1974 and U.S. Pat. No. 4,208,459, issued to HenryE. Becker, Albert L. McConnell, and Richard Schutte on Jun. 17, 1980,both of which are incorporated herein by reference. In general,uncompacted, nonpattern-densified tissue paper structures are preparedby depositing a papermaking furnish on a foraminous forming wire such asa Fourdrinier wire to form a wet web, draining the web and removingadditional water without mechanical compression until the web has afiber consistency of at least 80%, and creping the web. Water is removedfrom the web by vacuum dewatering and thermal drying. The resultingstructure is a soft but weak high bulk sheet of relatively uncompactedfibers. Bonding material is preferably applied to portions of the webprior to creping.

Compacted non-pattern-densified tissue structures are commonly known inthe art as conventional tissue structures. In general, compacted,non-pattern-densified tissue paper structures are prepared by depositinga papermaking furnish on a foraminous wire such as a Fourdrinier wire toform a wet web, draining the web and removing additional water with theaid of a uniform mechanical compaction (pressing) until the web has aconsistency of 25-50%, transferring the web to a thermal dryer such as aYankee and creping the web. Overall, water is removed from the web byvacuum, mechanical pressing and thermal means. The resulting structureis strong and generally of singular density, but very low in bulk,absorbency and in softness.

The tissue paper web of this invention can be used in any applicationwhere soft, absorbent tissue paper webs with high temporary wet strengthare required. One particularly advantageous use of the tissue paper webof this invention is in sanitary tissue products (e.g., toilet paper).

Analysis of the amount of treatment chemicals herein retained on tissuepaper webs can be performed by any method accepted in the applicableart. For example, the level of the quaternized amine-ester compound,such as an ester variation of a dialkyldimethylammonium salt, retainedby the tissue paper can be determined by solvent extraction of thecompound by an organic solvent followed by an anionic/cationic titrationusing Dimidium Bromide as indicator; the level of the wetting agent,such as PEG-400, can be determined by extraction in an organic solventfollowed by gas chromatography to determine the level of PEG-400 in theextract; the level of temporary wet strength resin such as a temporarywet strength resin with a nitrogen moiety (e.g., as described in U.S.Pat. No. 4,981,557, D. W. Bjorkquist issued Jan. 1, 1991) resin can bedetermined by subtraction from the total nitrogen level obtained via theNitrogen Analyzer, the amount of quaternized amine-ester compound level,determined by the above titration method. These methods are exemplary,and are not meant to exclude other methods which may be useful fordetermining levels of particular components retained by the tissuepaper.

Hydrophilicity of tissue paper refers, in general, to the propensity ofthe tissue paper to be wetted with water. Hydrophilicity of tissue papermay be somewhat quantified by determining the period of time requiredfor dry tissue paper to become completely wetted with water. This periodof time is referred to as "wetting time." In order to provide aconsistent and repeatable test for wetting time, the following proceduremay be used for wetting time determinations: first, a conditioned sampleunit sheet (the environmental conditions for testing of paper samplesare 23°±1° C. and 50±2% RH. as specified in TAPPI Method T 402),approximately 43/8 inch×43/4 inch (about 11.1 cm×12 cm) of tissue paperstructure is provided; second, the sheet is folded into four (4)juxtaposed quarters, and then crumpled into a ball approximately 0.75inches (about 1.9 cm) to about 1 inch (about 2.5 cm) in diameter; third,the balled sheet is placed on the surface of a body of distilled waterat 23°±1° C. and a timer is simultaneously started; fourth, the timer isstopped and read when wetting of the balled sheet is completed. Completewetting is observed visually.

The preferred hydrophilicity of tissue paper depends upon its intendedend use. It is desirable for tissue paper used in a variety ofapplications, e.g., toilet paper, to completely wet in a relativelyshort period of time to prevent clogging once the toilet is flushed.Preferably, wetting time is 2 minutes or less. More preferably, wettingtime is 30 seconds or less. Most preferably, wetting time is 10 secondsor less.

Hydrophilicity characters of tissue paper embodiments of the presentinvention may, of course, be determined immediately after manufacture.However, substantial increases in hydrophobicity may occur during thefirst two weeks after the tissue paper is made: i.e., after the paperhas aged two (2) weeks following its manufacture. Thus, the above statedwetting times are preferably measured at the end of such two weekperiod. Accordingly, wetting times measured at the end of a two weekaging period at room temperature are referred to as "two week wettingtimes."

The density of tissue paper, as that term is used herein, is the averagedensity calculated as the basis weight of that paper divided by thecaliper, with the appropriate unit conversions incorporated therein.Caliper of the tissue paper, as used herein, is the thickness of thepaper when subjected to a compressive load of 95 g/in² (14.7 g/cm²).

The following examples illustrate the practice of the present inventionbut is not intended to be limiting thereof.

EXAMPLE 1

The purpose of this example is to illustrate one method that can be usedto make soft, absorbent and high temporary wet strength tissue fibrousstructure treated with a mixture of Diester Dihydrogenated TallowDimethyl Ammonium Chloride (DEDTDMAC)(i.e., ADOGEN DDMC from the SherexChemical Company) and a polyethylene glycol wetting agent (i.e., PEG-400from the Union Carbide Company) in the presence of a temporary wetstrength resin in accordance with the present invention.

A pilot scale Fourdrinier papermaking machine is used in the practice ofthe present invention. First, a 1% solution of the chemical softenercomposition containing DEDTDMAC and PEG-400 is prepared according to thefollowing procedure: 1 . An equivalent molar concentration of DEDTDMACand PEG-400 is weighed; 2. PEG is heated up to about 180° F.; 3.DEDTDMAC is dissolved into PEG to form a melted solution; 4. Shearstress is applied to form a homogeneous mixture of DEDTDMAC in PEG; 5.The pH of the dilution water is adjusted to about 3 by the addition ofhydrochloric acid. 6. The dilution water is then heated up to about 180°F.; 7. The melted mixture of DEDTDMAC/PEG-400 is diluted to a 1%solution; and 8. Shear stress is applied to form an aqueous solutioncontaining a vesicle suspension of the DEDTDMAC/PEG-400 mixture.

Second, a 3% by weight aqueous slurry of NSK is made up in aconventional re-pulper. The NSK slurry is refined gently and a 2%solution of the temporary wet strength resin (as described in U.S. Pat.No. 4,981,557, D. W. Bjorkquist issued Jan. 1, 1991) is added to the NSKstock pipe at a rate of 0.75% by weight of the dry fibers. Theadsorption of the temporary wet strength resin onto NSK fibers isenhanced via an in-line mixer. The NSK slurry is diluted to about 0.2%consistency at the fan pump.

Third, a 3% by weight aqueous slurry of Eucalyptus fibers is made up ina conventional re-pulper. A 1% solution of the chemical softener mixtureis added to the Eucalyptus stock pipe before the stock pump at a rate of0.2% by weight of the dry fibers. The adsorption of the chemicalsoftener mixture to the Eucalyptus fibers can be enhanced via an in-linemixer. The Eucalyptus slurry is diluted to about 0.2% consistency at thefan pump.

The treated furnish mixture (30% of NSK/70% of Eucalyptus) is blended inthe head box and deposited onto a Fourdrinier wire to form an embryonicweb. Dewatering occurs through the Fourdrinier wire and is assisted by adeflector and vacuum boxes. The Fourdrinier wire is of a 5-shed, satinweave configuration having 87 machine-direction and 76cross-machine-direction monofilaments per inch, respectively. Theembryonic wet web is transferred from the Fourdrinier wire, at a fiberconsistency of about 15% at the point of transfer, to a photo-polymerbelt having 562 Linear Idaho cells per square inch, 32 percent ofknuckle areas and 6 mils of photo-polymer depth. Further dewatering isaccomplished by vacuum assisted drainage until the web has a fiberconsistency of about 28%. The patterned web is predried by airblow-through to a fiber consistency of about 65% by weight. The web isthen adhered to the surface of a Yankee dryer with a sprayed crepingadhesive comprising 0.25% aqueous solution of Polyvinyl Alcohol (PVA).The fiber consistency is increased to an estimated 98% before the drycreping the web with a doctor blade. The doctor blade has a bevel angleof about 24 degrees and is positioned with respect to the Yankee dryerto provide an impact angle of about 83 degrees; the Yankee dryer isoperated at about 800 fpm (feet per minute) (about 244 meters perminute). The dry web is formed into roll at a speed of 700 fpm (214meters per minute).

Two plies of the web are formed into tissue paper products andlaminating together using conventional ply bonding techniques well knownin the papermaking industry. The tissue paper has about 23 lbs./1000 sq.ft. basis weight, contains about 0.05% of DEDTDMAC, 0.05% PEG-400, andabout 0.5% of the temporary wet strength resin. Importantly, theresulting tissue paper is soft, absorbent and has high temporary wetstrength.

EXAMPLE 2

The purpose of this example is to illustrate one method that can be usedto make soft, absorbent and high temporary wet strength tissue fibrousstructure treated with a mixture of Diester Dihydrogenated TallowDimethyl Ammonium Chloride (DEDTDMAC) and a linear ethoxylated alcoholwetting agent (i.e., Neodol 23-7 from the Shell Chemical Company) in thepresence of a temporary wet strength resin in accordance with thepresent invention.

The tissue structure is produced in accordance with the hereinbeforedescribed process of Example 1 with the exception that an equivalentmolar concentration of Neodol 23-7 is used as the wetting agent insteadof PEG-400. The resulting tissue paper contains about 0.05% DEDTDMAC,0.05% Neodol 23-7, and about 0.5% of the temporary wet strength.Importantly, the tissue paper is soft, absorbent and has high temporarywet strength.

EXAMPLE 3

The purpose of this example is to illustrate one method that can be usedto make soft, absorbent and high temporary wet strength tissue fibrousstructure treated with a mixture of Diester Dihydrogenated TallowDimethyl Ammonium Chloride (DEDTDMAC) and a linearalkylphenoxypoly(ethyleneoxy) alcohol (Igepal RC-520) in the presence ofa temporary wet strength resin in accordance with the present invention.

The tissue structure is produced in accordance with the hereinbeforedescribed process of Example 1 with the exception that an equivalentmolar concentration of Igepal RC-520 (a lineardodecylphenoxypoly(ethyleneoxy) alcohol with about 5 moles ethyleneoxide per mole of dodecylphenol) is used as the wetting agent instead ofPEG-400. The resulting tissue paper contains about 0.05% DEDTDMAC, 0.05%Igepal RC-520, and about 0.5% of the temporary wet strength.Importantly, the tissue paper is soft, absorbent and has high temporarywet strength.

What is claimed is:
 1. A strong, soft, absorbent biodegradable tissuepaper web comprising:(a) papermaking fibers; (b) from about 0.01% toabout 2.0% by weight of a biodegradable quaternized amine-estersoftening compound having the formula ##STR13## and mixtures thereof;wherein each R substituent is a C₁ -C₆ alkyl or hydroxyalkyl group, ormixtures thereof; R¹ is ##STR14## or a C₁₃ -C₁₉ hydrocarbyl group ormixtures thereof; R² is a C₁₃ -C₂₁ hydrocarbyl group, or mixturesthereof; and X⁻ is a compatible anion; (c) from about 0.01% to about2.0% by weight of a polyhydroxy compound selected from the groupconsisting of glycerol and polyethylene glycols having a molecularweight from about 200 to about 2000; and (d) from about 0.01% to about3.0% by weight of a water-soluble temporary wet strength resin.
 2. Thepaper web of claim 1 wherein said polyhydroxy compound is a polyethyleneglycol having a molecular weight from about 200 to about
 600. 3. Thepaper web of claim 2 wherein said quaternized amine-ester softeningcompound is ##STR15##